Hi all,
Some great input here! My preference would be to improve the semantics and accessibility with html5 elements in combination with WAI-ARIA Landmark Roles, and to simplify and refine the html and css. Beauty is, of course, in the eye of the beholder but a minimal design ethic can be incredibly effective, provide a clean and refreshing working environment that assists rather than detracts from the task at hand.
Personally, I would avoid the use of Bootstrap in this case because, as others have already correctly pointed out, there are known accessibility issues with Bootstrap in it's current form, Bootstrap is rapidly evolving so there are upgrade issues as soon as it is incorporated, bringing a maintenance requirement that we don't currently have with Hathor as it 'Just works' and will continue to do so as long as it is built with W3C standard html and css.
I have to agree with Mareike on this, the accessible template should be as bullet-proof as it can possibly be. Independent, accessible and future-friendly. That is going to be *very* hard to do with Bootstrap. As Angie mentions, template overrides could be used to improve the accessibility and semantics of core outputs.
If this were my project I would be looking firstly at the accessibility and semantics of the underlying code, and then at things like typography (heirachy, intent, readability) and style (flat, high-contrast, well-spaced).
Best regards,
Seth